Sharpness at 135mm

For this review, the sharpness test is carried out by photographing a real-world sample, rather than a test chart. The Canon EF 70-300mm f/4-5.6 IS II USM Lens was mounted on a Canon EOS 5D Mark IV, which was in-turn mounted to a sturdy tripod. Exposure delay mode was activated to prevent camera-shake. Any changes in tone you might see across the crops are due to natural light changes during the shooting session.

The full frame at 135mm

At the 135mm focal length, sharpness at the centre is very good at the widest aperture of f/5, being a touch sharper at f/5,6, where it remains excellent up until f/16. At f/22, it’s ever so slightly softer, while at f/32 and f/40 (the narrowest aperture), the softness is more obvious. You may not notice too much at normal printing and web sizes, but there’s not much advantage to shooting at these kind of apertures. At the edges, the sharpest images are at f/16 and f/22.